Medical injector with coupled body portions

ABSTRACT

A medical injector is provided herein which includes first and second body portions each having a longitudinal axis and configured to couple at a coupling. The first and second body portions are complementarily formed so as to be movable about the coupling. The medical injector also includes an axially-displaceable plunger; biasing element for advancing the plunger a predetermined distance; and, a releasable retainer for releasably retaining the plunger in a first state against the force of the biasing element. In an initial state, the axes of the first and second body portions are not aligned and the plunger is in the first state. In a coupled state, the axes of the first and second body portions are axially aligned, and the releasable retainer releases the plunger, thereby allowing the biasing element to advance the plunger the predetermined distance. Advantageously, the subject invention provides a medical injector having an automated plunger drive which is triggered upon assembly of the pen injector, thereby minimizing premature or failed activations.

FIELD OF THE INVENTION

This invention relates to medical injectors, and, more particularly, tomedical injectors having plunger drive mechanisms.

BACKGROUND OF THE INVENTION

Medical injectors are well known in the prior art, including injectorswhich have internal drive mechanisms for plunger advancement. Plungeradvancement may be utilized to conduct automated reconstitution of atwo-or more part medicament and/or to cause automated injection. Morespecifically, the automation of plunger advancement may be utilized tocause combination of a multiple part (e.g., wet/dry) medicament. Inaddition, or alternatively, the automated advancement of the plunger maycause a needle to be advanced for injection and/or medicament to bedriven through the needle during injection. Such automated actionrequires a trigger mechanism. Concerns exist over premature or failedtrigger activation.

SUMMARY OF THE INVENTION

A medical injector is provided herein which includes first and secondbody portions each having a longitudinal axis and configured to coupleat a coupling. The first and second body portions are complementarilyformed so as to be movable about the coupling. The medical injector alsoincludes an axially-displaceable plunger; biasing element for advancingthe plunger a predetermined distance; and, a releasable retainer forreleasably retaining the plunger in a first state against the force ofthe biasing element. In an initial state, the axes of the first andsecond body portions are not aligned and the plunger is in the firststate. In a coupled state, the axes of the first and second bodyportions are axially aligned, and the releasable retainer releases theplunger, thereby allowing the biasing element to advance the plunger thepredetermined distance. Advantageously, the subject invention provides amedical injector having an automated plunger drive which is triggeredupon assembly of the pen injector, thereby minimizing premature orfailed activations.

These and other features of the subject invention will be betterunderstood through a study of the following detailed description andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show a medical injector formed in accordance with thesubject in pre-assembled and assembled states, respectively;

FIGS. 3 and 4 are cross-sectional views of a medical injector formed inaccordance with the subject invention;

FIG. 5 is a schematic of a releasable retainer useable with the subjectinvention;

FIG. 6 is a cross-sectional view of a medical injector formed inaccordance with the subject invention having a reservoir configured forreconstitution;

FIGS. 7 and 8 show an arrangement for achieving relative movement ofcomponents;

FIG. 9 is an exploded view of components useable with the subjectinvention;

FIG. 10 is a cross-sectional view taken along line 10-10 of FIG. 9;

FIG. 11 is a perspective view of a dose knob useable with the subjectinvention;

FIG. 12 is an exploded view of the subject invention;

FIGS. 13-16 show operation of a medical injector formed in accordancewith the subject invention; and

FIGS. 17-20 show cap configurations useable with the subject invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the figures, a medical injector is shown and generallydesignated with the reference numeral 10. The medical injector 10 may beof various types, but preferably is of the pen injector type. Themedical injector 10 may be used to administer various injectableliquids, particularly medicaments.

With reference to FIG. 1, the medical injector 10 includes first andsecond body portions 12, 14 which are connected through a movementrelative to coupling 16. Preferably, the coupling 16 is a hingedconnection. The first and second body portions 12, 14 arecomplementarily formed so as to be assembled together with sufficientmovement, e.g., rotation, about the coupling 16. As shown in FIG. 1,longitudinal axes L1, L2 of the first and second body portions 12, 14are not axially (not collinearly) aligned in an initial state of themedical injector 10. The assembled state of the medical injector 10 isshown in FIG. 2 where the longitudinal axes L1, L2 are axially aligned.

The first and second body portions 12, 14 are preferably formed of rigidmaterial and to varying extents accommodate different portions of themedical injector 10. Preferably, to facilitate assembly, as shown inFIG. 3, a reduced diameter portion 18 is formed on one of the first andsecond body portions 12, 14 with a corresponding telescoping portion 20being formed on the other of the first and second body portions 12, 14.In this manner, the first and second body portions 12, 14 may beassembled with the telescoping portion 20 being disposed over thereduced diameter portion 18. In addition, cooperating locking elements22, such as cooperating detent and groove, meshing teeth, and/or othersnap-together locking features, may be provided to lock the first andsecond body portions 12, 14 together once assembled.

As shown in the figures, particularly FIGS. 7 and 8, the coupling 16 maybe a pin hinge where brackets 24 are provided on the first and secondbody portions 12, 14 which are joined together to rotate about a centralpin 26. As will be appreciated by those skilled in the art, a livinghinge may also be used for the coupling 16. The coupling 16 ispositioned and formed to allow proper movement, e.g., rotation,thereabout in allowing the first and second body portions 12, 14 to cometogether and form the medical injector 10.

The medical injector 10 includes an axially-displaceable plunger 28. Theplunger 28 may be formed as a single piece or by modular components. Themodular components may be fixed to one another or located adjacently,but not connected, so as to move together. In a preferred embodiment,the plunger 28 is initially located in the second body portion 14. Abiasing element 30 is also provided configured and positioned to advancethe plunger 28 a predetermined distance. Preferably, the biasing element30 is a compression or coil spring, but other biasing elements maylikewise be utilized. Preferably, the biasing element 30 is positionedin the second body portion 14.

A releasable retainer 32 is provided configured and positioned toreleasably retain the plunger 28 in an initial first state against theforce of the biasing element 30. The releasable retainer 32 isconfigured such that, upon assembly of the first and second bodyportions 12, 14, the releasable retainer 32 releases the plunger 28thereby allowing the biasing element 30 to advance the plunger 28 thepredetermined distance. As will be appreciated by those skilled in theart, various releasable retainers may be used with the subjectinvention.

It is preferred that the plunger 28 be advanced in a distal direction.As used herein, distal refers to a direction towards a patient duringuse, while proximal refers to a direction away from a patient duringuse.

By way of non-limiting example, the releasable retainer 32 may be adisplaceable cam member 34, as shown in FIGS. 3-5. As shown in FIGS. 3and 4, upon assembly of the first and second body portions 12, 14, a camarm 36 may be displaced, such as by interfering engagement with aportion or component of the first body portion 12, thus causingdisplacement of the cam member 34. The cam member 34 may include aprotruding stop member 38 formed to interferingly engage a portion ofthe plunger 28, such as shoulder 40, in causing retention thereof in aninitial, first state, before use. With displacement of the cam member34, the cam member 34 releases the shoulder 40 thus allowing the biasingelement 30 to drive the plunger 28 distally. It is preferred that thecam member 34 be pivotally connected to the second body portion 14, soas to be rotatable relative thereto. Displacement of the cam member 34may be achieved by interengagement of ramped surface 42 of the cam arm36 acting against engagement surface 44 of the cam member 34 undermovement of the cam arm 36 resulting in sufficient rotation of the cammember 34 to clear the stop member 38 from the shoulder 40.

The medical injector 10 includes a reservoir 46 disposed in the firstbody portion 12 formed to accommodate medicament or other substance 48for injection into a patient. As shown in FIG. 3, the reservoir 46 maybe a single chamber disposed in a barrel 50 sealed at a proximal end bya septum 52 and sealed at a distal end by a stopper 54 which is formedto be slidable through the barrel 50 for urging the substance 48therefrom, as known in the art. The medical injector 10 also includes aneedle mounting surface 56 having features 58 formed thereon formounting a needle 60 thereto. The needle 60 may include a hub 62 havingmounting features 64 provided thereon for cooperative engagement withthe features 58 in mounting the needle 60 to the needle mounting surface56. The features 58 and the mounting features 64 may be of any knowncooperating elements which permit a mechanical connection therebetween,such as threads or bayonet lock, and/or a frictional interengagement,such as a Luer mounting. The needle mounting surface 56 may be formed onthe first body portion 12 or a component thereof.

The needle 60 also includes a needle cannula 61 having a distal end 63,formed for insertion into a patient, and a proximal end 65.

The reservoir 46 may be configured to accommodate multiple componentswhich are mixable for reconstitution. For example, as shown in FIG. 6,the reservoir may accommodate first and second mixable components 66,68. The stopper 54 may be associated with the reservoir 46 such thatdistal advancement of the stopper 54 over a predetermined distance shallcause mixing of the first and second mixable components 66, 68. Anyknown arrangement for allowing such mixing may be utilized. By way ofnon-limiting example, the first and second mixable components 66, 68 maybe separated by a secondary stopper 70. The secondary stopper 70 dividesthe reservoir 46 into first and second chambers 72, 74, respectively,accommodating the first and second mixable components 66, 68. The septum52 seals off the distal end of the first chamber 72, while the stopper54 is positioned to seal off the proximal end of the second chamber 74.Preferably, if a dry component is used as one of the mixable components,the dry mixable component is located in the first chamber 72.

One or more by-pass channels 76 are formed in the wall of the reservoir46. In an initial state, as shown in FIG. 6, the secondary stopper 70 islocated at least partially proximally of the by-pass channels 76 so asto define a seal between the first and second chambers 72, 74 and todefine a seal between the second chamber 74 and the by-pass channels 76.With distal advancement of the stopper 54, and with the second mixablecomponent 68 being wet and generally incompressible, force of movementof the stopper 54 is transmitted to the secondary stopper 70 through thesecond mixable component 68. With sufficient distal movement of thesecondary stopper 70, the second chamber 74 comes into communicationwith the by-pass channels 76, thus allowing the second mixable component68 to be urged into the first chamber 72 with further distal movement ofthe stopper 54. With sufficient distal advancement of the stopper 54,the second chamber 74 is collapsed with none or substantially none ofthe second mixable component 68 remaining therein. In addition, thesecondary stopper 70 is located so as to define a seal between the firstchamber 72 and the by-pass channels 76. The first and second mixablecomponents 66, 68 are mixed within the first chamber 72, such as throughagitation of the medical injector 10, so as to produce the injectablesubstance 48, ready for injection.

The barrel 50 of the reservoir 46 may be the barrel of a separate drugcartridge, as shown in the figures, or a portion of the medical injector10, particularly the first body portion 12.

As will be recognized by those skilled in the art, other arrangementsfor permitting reconstitution may be utilized. In addition, more thantwo-part systems, such as three-part and so forth, systems may beutilized. Active medical ingredients may be included in one or both ofthe first and second mixable components 66, 68. The first mixablecomponent 66 may be dry (e.g., a powder or granular substance) and/or aliquid (e.g., flowable (slurry or liquid)). As mentioned above, thesecond mixable component 70 is preferably only a wet flowable component,such as a liquid or slurry.

Distal advancement of the plunger 28 under force of the biasing element30 may be used to achieve one or more objectives. The plunger 28 isconfigured to act against the stopper 54 and cause displacement thereof.With the reservoir 46 being configured for reconstitution,autoreconstitution of the contents of the reservoir 46 may be achieved.In addition, or alternatively, the medical injector 10 may be configuredto be an autoinjector, where the needle 60 is initially housed withinthe first body portion 12 and forced thereout of under force of thebiasing element 30 so as to pierce a patient's skin, e.g., with forwardmovement of the reservoir 46, as known in the art. In addition, oralternatively, distal advancement of the plunger 28 may causeadministration of the contents of the reservoir 46 through the injectedneedle.

Depending on the desired effect, the medical injector 10 may beconfigured to have the plunger 28 be driven a predetermined distance. Aphysical stop, such as interengagement between the shoulder 40 and aproximal end 78 of the reservoir 46 (e.g., proximal end of the barrel50), may be employed to limit distal advancement of the plunger 28.Under certain circumstances, the plunger 28 may be distally advancedwithout the needle 60 being mounted to the medical injector 10. Thus,the reservoir 46 is not vented during such action. With the needle 60being subsequently mounted to the reservoir 46, any residual gasestrapped in the reservoir 46 are purged through the needle 60. It may bepreferred to not provide a physical stop to the distal advancement ofthe plunger 28. In this manner, the contents of the reservoir 46 may bemaximally compressed under force of the biasing element 30. Withsubsequent mounting of the needle 60 onto the medical injector 10, thereservoir 46 is vented thus permitting further distal advancement of theplunger 28. This secondary distal advancement may assist in priming theneedle 60 for use.

FIG. 6 shows the medical injector 10 in a state prior to use. As showntherein, the reservoir 46 may be a drug cartridge which is separablefrom the first body portion 12. One or more cartridge retaining hooks 80may be provided to act against the barrel 50 in holding the barrel 50 inthe first body portion 12. It is preferred that the cartridge retaininghooks 80 be resilient so as to permit outward deflection in loading thereservoir 46 into the first body portion 12.

It is preferred that a cartridge retaining element 82 be provided whichincludes a sleeve 84 into which the reservoir 46 is disposed. Inaddition, it is preferred that the needle mounting surface 56 and thecartridge retaining hooks 80 be formed on the cartridge retainingelement 82. The cartridge retaining element 82 may be retained in thefirst body portion 12 through any known fixing arrangement, such as amechanical connection, e.g., snap engagement or frictional connections,and/or chemical or adhesive connections, such as fusion, welding orgluing.

Movement of one or more of the components relative to the first and/orsecond body portions 12, 14 may be desired. To obtain such relativemovement, with reference to FIGS. 7 and 8, a pinion 86 may be mounted toone of the first and second body portions 12, 14 with a correspondingrack 88 being mounted to the component intended for relative movement.As shown in the Figures, the cartridge retaining element 82 may beconfigured for movement relative to the first body portion 12. To thisend, the cartridge retaining element 82 may be nested within the firstbody portion 12 with the rack 88 being located thereon. The pinion 86and the rack 88 are formed with teeth 87, 89 formed for cooperatingmeshing engagement. With movement about the coupling 16, the pinion 86rotates and causes linear translation of the rack 88, thus causing thecartridge retaining element 82 to translate relative to the first bodyportion 12. This linear translation permits for various axialadjustments of the reservoir 46, or other components. The needlemounting surface 56 may be formed on the cartridge retaining element 82and caused to be initially hidden in the first body portion 12 (FIG. 1)with subsequent distal advancement through translation of the cartridgeretaining element 82 causing the needle mounting surface 56 to becomeexposed (FIG. 2). In this manner, control can be established over propertiming of the needle mounting surface 56 during sequence of preparationof the medical injector 10. In particular, it may be desired to exposethe needle mounting surface 56 only after reconstituting, ifreconstitution is utilized.

The medical injector 10 may be a fixed dose injector configured toadminister single or multiple fixed doses. In addition, the medicalinjector 10 may be configured to permit dose setting for either a singleor multiple doses. In a preferred embodiment, the medical injector 10 isa single, variable-dose autoreconstitution injector.

As will be appreciated by those skilled in the art, variousconfigurations to permit dose setting may be utilized. By way ofnon-limiting example, and with reference to FIGS. 9 and 10, a knob stem90 may be provided with a plurality of axially and radially spaced-apartabutment surfaces 92.

The abutment surfaces 92 are axially alignable with an engagementsurface 94 formed on the plunger 28 such that with sufficient distaldisplacement of the knob stem 90 at least one of the abutment surfaces92 will be caused to engage the engagement surface 94 and transmit forceof movement to the plunger 28. In this manner, distal displacement ofthe knob stem 90 may be transmitted to the plunger 28. Moreover, strokelength corresponding to the movement of the plunger 28 may be adjusteddepending on the abutment surface 92 which is in engagement with theengagement surface 94. The greater the initial distance of the abutmentsurfaces 92 from the engagement surface 94, the corresponding smallerdose that will be caused to be administered. Regardless of the selecteddose amount, it is preferred that the knob stem 90 having a fixed lengthof stroke for distal displacement during administration of an injection.The further abutment surfaces 92 have greater lost motion with distalmovement of the knob stem 90 and, thus, less distance engaging theengagement surface 94. The extent of movement of the plunger 28 dictatesthe extent of movement of the stopper 54 and, thus, dictates the amountof the injectable solution 48 to be driven from the reservoir 46 in aninjected dose.

The dose is selected by rotating a dose knob 96 which is fixed to theknob stem 90 so as to rotate therewith. The dose knob 96 and the knobstem 90 can be connected through any known manner, including throughcooperating mechanical elements. To prevent the dose knob 96 from beinginadvertently turned prior to proper preparation of the medical injector10, such as prior to mixing of the mixable components 66, 68, assemblyof the first and second body portions 12, 14, and so forth, the knobstem 90 may be coupled to the plunger 28 so as to prevent relativerotation therebetween with the plunger 28 being non-rotatably coupled tothe second body portion 14. With reference to FIG. 9, the plunger 28 mayhave one or more lobes 98 formed to nest in corresponding channels 100formed in the second body portion 14. The plunger 28 may slide along thechannels 100 without rotating relative thereto. In turn, the plunger 28may have one or more internal slots 102 in which are initially nestedcorresponding splines 104 protruding from the plunger 28. With distaladvancement of the plunger 28, the plunger 28 may decouple from the knobstem 90 so as to permit relative rotation therebetween.

In addition, with reference to FIGS. 9 and 10, a groove 106 may beformed in the knob stem 90 corresponding to a rib 108 formed on theplunger 28. In an initial state, the rib 108 nests within the groove 106so as to prevent relative rotation between the plunger 28 and the knobstem 90. With distal advancement of the plunger 28 being completed, suchas with completed reconstitution, the plunger 28 may be advanced so asto have the rib 108 removed from the groove 106 and to have the spline104 removed from the internal slot 102. The knob stem 90 is then free torotate in setting a dose. Alternatively, the rib 108 may still bepartially nested in the groove 106 even after distal advancement of theplunger 28, such as to a post-reconstituted state. With thisconfiguration, the knob stem 90 may be proximally displaced to have therib 108 removed from the groove 106 thus permitting subsequent dosesetting. The dose is administered by causing distal advancement of theknob 90 once the dose has been properly set.

It is noted that the engagement surface 94 may be located at a proximalend 110 of the rib 108.

It is preferred that the dose knob 96 be releasably retained inpositions corresponding to the various dose settings. In this manner, itis preferred that once a dose has been set, there is no rotation of thedose knob 96 during distal displacement thereof, thus avoiding that animproper of the abutment surfaces 92 engage the engagement surface 94.Such an arrangement is disclosed in U.S. Pat. No. 6,793,646. As shown inU.S. Pat. No. 6,793,646, and with reference to FIGS. 11 and 12, one ormore tabs 110 may be formed on the dose knob 96 which are selectivelyengageable with one or more positioning channels 112 formed on thesecond body portion 14. The positioning channels 112 may becircumferentially spaced apart and positioned to represent dose settingscorresponding to the abutment surfaces 92. The tabs 110 nest in thepositioning channels 112 at given radial positions of the dose knob 96corresponding to different dose sizes. With turning of the dose knob 96,the tabs 110 are caused to by-pass the dose positioning channels 112.The positioning channels 112 maintain the radial position of the doseknob 96.

In addition, it is preferred that the dose knob 96 be limited in axialmovement so as to permit a fixed stroke length of distal advancement fordose administration. The second body portion 14 may be provided with areduced diameter opening 116 sized and positioned to interferinglyengage the knob stem 90 upon a predetermined extent of proximalmovement. The stroke of an injection is defined by the extent ofproximal movement of the knob stem 90.

For use, the medical injector 10 is initially presented in the stateshown in FIG. 1, where the first and second body portions 12, 14 areseparated. To prepare for use, the first and second body portions 12, 14are moved about the coupling 16 so as to come to the assembled stateshown in FIG. 2. It is preferred that no needle be mounted to themedical injector 10 prior to assembly. With assembly, the plunger 28 iscaused to be distally advanced under force of movement by the biasingelement 30. Reconstitution and/or other effects are achieved throughthis automated movement. Thereafter, the needle 60 is mounted to themedical injector 10 as shown in FIG. 13. The needle 60 may be providedwith a cap or shield 60A. Any gases trapped in the reservoir 46 arepurged through the needle 60 and the needle 60 may be primed for use.

With reference to FIGS. 14 and 15, a dose may be selected by proximallywithdrawing the dose knob 96. Proximal withdrawal of the dose knob 96 islimited, as described above. Once withdrawn, the dose knob 96 may berotated to a desired setting. Indicia 116 may be provided to representdoses. The indicia 116 may include numeral representations and a pointeror other indicator. With reference to FIG. 16, the needle 60 is causedto pierce the skin of a patient and the dose knob 96 is then depressedto cause the knob stem 90 to advance distally. Interengagement betweenthe selected of the abutment surfaces 92 and the engagement surface 94causes the plunger 28 to drive the stopper 54 in administering aninjection.

With the pre-use assembly of the medical injector 10, a cap 118 may beprovided to cover at least partially the first and second body portions12, 14, particularly about the coupling 16 as shown in FIGS. 17-20.

The cap 118 may be formed of a rigid material with a general cup shape.A loading aperture 120 may be formed in the cap 118 positioned over thefirst body portion 12 so as to allow the reservoir 46 to passtherethrough and be loaded into the first body portion 12. In thismanner, a medical injector 10 may be stored without the reservoir 46being located therein. The reservoir 46 may be loaded into the medicalinjector 10 without the cap 118 having to be removed therefrom. Inaddition, the cap 118 may be formed to accommodate one or more of theneedles 60 therein. To maintain a clean and sterile environment withinthe cap 118, a sterility barrier 122, such as a removable film, ispreferably provided to cover the loading aperture 120. The cap 118 mayalso be configured to form a tight seal about the medical injector 10. Acomplimentary compartment 124 may be provided with the cap 118 to whollyenclose the medical injector 10.

1. An injection device comprising: first and second body portions eachhaving a longitudinal axis and configured to couple together at acoupling, said first and second body portions being complementarilyformed so as to be movable about said coupling; an axially-displaceableplunger; biasing means for advancing said plunger a predetermineddistance; and a releasable retainer for releasably retaining saidplunger in a first state against the force of said biasing means,wherein, in an initial state, said axes of said first and second bodyportions are not axially aligned and said plunger is in said firststate, and wherein, in a coupled state, said axes of said first andsecond body portions are axially aligned and said releasable retainerreleases said plunger thereby allowing said biasing means to advancesaid plunger said predetermined distance.
 2. An injection device as inclaim 1, wherein said coupling is a hinged connection.
 3. An injectiondevice as in claim 2, wherein said first and second body portions arerotatable about said hinged connection.